There is a library on Particle Build for it and I remember some thread on this forum about it
https://build.particle.io/libs/564a45ef3532208b19001042/tab/Adafruit-CAP1188.cpp
A quick search on here CAP1188 would have come up with
capTouch(cap1188) + photon
Working on getting capacitive touch sensor (CAP-1188) to register single and multiple clicks